The invention relates to hose clips in general, and more particularly to improvements in hose clips of the type wherein a strap surrounds a tightening or clamping insert or shield and the insert is biased against the peripheral surface of a hose by one or more springs.
European Pat. No. 0 166 756 B1 to Enlund discloses a hose clip which includes a corrugated spring with axially parallel undulations or corrugations. The spring is intended to automatically compensate for variations of tightening, tensioning or clamping action upon the confined part of a hose. Such variations can develop as a result of changes of elasticity of the hose, e.g., in response to heating or cooling. The just outlined situation will develop when the hose is used to convey streams of a cool fluid medium as well as streams of a hot fluid medium. Furthermore, the elasticity of the hose is likely to change as a result of aging. In all such instances, the corrugated spring is expected to automatically compensate for variations of elasticity of the hose and to thus ensure that the hose is reliably clamped without necessitating manual adjustment of clamping action by rotating a screw or bolt (reference may be had, for example, to commonly owned U.S. Pat. No. 4,627,645 to Sauer) or by tightening the strap around the hose in another way (reference may be had, for example, to commonly owned U.S. Pat. No. 4,523,352 to Wachter).
It has been found that, in many instances, heretofore known hose clips cannot compensate for all (i.e., for an entire range of) fluctuations of clamping force upon the hose. In addition, variations of the clamping force cannot always be detected as soon as they develop, for example, if such variations are attributable to heating or cooling of a metallic pipe or tube which is surrounded by a hose which, in turn, is surrounded by the strap of a hose clip. Still further, pronounced variations of clamping force upon a hose are likely to take place in response to substantial and prolonged rise of temperature of the hose as well as when the hose is subject to permanent deformation (for example, as a result of the application of a large tensioning or tightening while the temperature of the hose varies within a wide range). Under such circumstances, the material of the hose is likely to flow from within the area which is surrounded by the strap of the hose clip. An undulate spring of the type disclosed in the patent to Enlund is highly unlikely to automatically compensate for a full range of variations of clamping force under the aforediscussed circumstances. Thus, it is necessary to reduce the diameter of the strap, e.g., by manually adjusting the angular position of a screw or bolt or by manually adjusting the position of another strap tightening device.
Any variations of the diameter of the strap necessitate a shifting of a portion of the strap circumferentially of the hose. This can create problems when a hose clip of the type disclosed by Enlund has been in use for an extended period of time because the internal surface of the strap and/or the internal surface of the clamping insert is likely to adhere to the peripheral surface of the hose as a result of the application of a pronounced clamping force and/or in response to the application of pronounced thermal stresses. In many instances, the strap and/or the insert adheres to the hose with a force which cannot be readily overcome by the strap and/or by the insert, i.e., not even a small portion of the strap is capable of moving relative to and in the circumferential direction of the hose so that the entire hose clip must be replaced or the strap and the insert are incapable of ensuring the establishment and maintenance of a requisite clamping or tightening force. In other words, the hose is likely to permit leakage of confined fluid medium as a result of the application of varying thermal stresses and/or as a result of aging (reduction of elasticity) of the material of the hose. The fluid medium escapes between the internal surface of the hose and a pipe, tube, nipple or other rigid conductor of fluid media.
The situation is substantially the same if the insert and the spring, which operates between the insert and the strap, are replaced with one or more springs (e.g., coil springs or packages of dished springs) which react against the housing of a strap tightening device and bear against the head of, or a nut on, the shank of a rotary tightening bolt or screw. Thus, once the strap begins to adhere to the peripheral surface of the hose, it cannot slide in the circumferential direction of the hose in response to tightening of the bolt or screw, i.e., the hose clip cannot compensate for variations of the tightening or clamping action upon the hose.
European Pat. No. E 34 206 B to Ribrant discloses a hose clip wherein the insert is a circumferentially complete strip which is surrounded by a wire-like or strip-shaped strap. A screw is used to tighten the strap around the insert. The internal surface of the insert will begin to adhere to the external surface of the hose after a certain period of use of the patented strap, especially if the hose is subjected to a pronounced tightening or clamping action and its temperature varies within a rather wide range.
Published German patent application No. 1 525 495 of Oetiker discloses a hose clip wherein the strap is provided with a plurality of integral or separately produced springs. The springs are supposed to increase the tightening or clamping action upon a hose which is likely to lose elasticity due to aging or as a result of the application of pronounced thermal stresses. The internal surface of the strap is likely to permanently adhere to the external surface of the hose and to thus prevent automatic, or even manual, adjustment of the clamping or tightening action.
British Pat. No. 1.138.064 to Nicholson discloses a band clamp or hose clip with a band or strap which is adjustable by means of a worm or T-bolt, and a bedding band or insert inside the adjustable band. The adjustable band has one or more lateral corrugations so that it is capable of self-contraction in order to maintain a desired radially inward pressure. The insert or bedding band is likely to strongly adhere to the external surface of a hose in response to aging of the material of the hose and/or in response to prolonged application of pronounced tightening or clamping (radially inward) forces.
U.S. Pat. No. 2,666,004 to Gerrard discloses a steel strapping and shield which can be used to bias insulating and/or structural members on tanks, vessels and the like. The strapping comprises a metallic expander band with corrugated and uncorrugated sections, a shield which can be inserted between the corrugated sections and one or more structural members, and a device which detachably mounts the shield on the expander band and can be applied subsequent to mounting of the band. The patented apparatus cannot be classified as a hose clip since its principal purpose is to secure insulation to tanks or similar large and bulky structures which expand and contract under various physical changes, such as temperature changes. The purpose of the shield which is disclosed by Gerrard is to prevent the segments of the corrugated sections from acting like saw teeth during the cyclic change of expansion and contraction when the expander band is mounted over soft, porous insulating material. A hose clip is not mounted over a porous material because this would defeat the purpose of the hose clip, namely to establish a fluidtight connection between a hose and a pipe, tube, nipple or the like.
German Utility Model No. G 89 03 321.3 to Anderstorps Werkstads AB discloses a hose clip wherein a split ring of spring steel has a U-shaped cross-sectional outline with a convex side facing the part to be clamped. The end portions of the split ring can be indirectly moved toward or away from each other by a screw or bolt. The split ring has two marginal flanges or legs which are provided with notches to form a series of identical teeth. The split ring is surrounded by a strap, one end portion of which is secured to the housing for the nut or bolt, and the other end portion of which has teeth mating with the thread of the screw or bolt. The convex inner side of the split ring is pressed against and is likely to adhere to the external surface of a hose when the strap is tightened and its diameter is reduced to thereby reduce the diameter of the split ring.